Bomb fuze, centrifugal-inertia type



June 5, 1956 E. P. BERTRAM 2,748,708

BOMB FUZE, CENTRIFUGAL.-INERTIA TYPE Filed Nov. 2, 1951 I l 43 42 E@ 1,2 2:20 E@ JNVENTOR. Emil 1:. BEDPun-L ATTORNEYS BONIB FUZE, CENTRIFUGAL-INERTIA TYPE Emil P. Bertram, Wilmington, (lhio,l assigner. to the United States of America as represented'by the Secretary ofthe Army Application November 2, 1951, Serial No. 254,622.'

7 Claims. (Cl. 102-79)v (Granted under Title 35, U. S. Code (i952), sec. 266) This invention may be manufactured and used forithe Government, for governmental purposes, without payment to me of any royalties thereon.

The present invention relates t fuzes and moreparticularly to automatic arming means for a fuze employable on bombs.

In the past such fuzes have had functional requirements of minimum and maximum air travel distances, minimum andmaximum air velocities, or combinations thereof for arming. Current designs for accomplishment. of these requisites generally involve extensive gear trains to obtain reduction of relatively high impeller speeds. Such designs result in high manufacturing costs and excessive production time, while at the same time presenting a greater failure potential d ue to the large number of movingrcomponeuts.

it is AaV primary object of this inventionto provide a fuze, which ycan be manufactured more cheaply and expeditiously thancurrently employed types.

Another important object is to provide a fuze inwhich the failure potential is decreased considerably by reason of the simplification of structure, especially in regard to deletion of reduction gear trains.

Another object is to provide a basic fuze design which can be adapted to allow maximum flexibility of application-and operation to meet special requirements dictated by such variables as size and type of bombs wherewith,

the fuze is to be used.

Still another object of this invention is to simplify. fuze structure by utilizing a firing pin as a rotor lock andras an axis .member for an impeller in addition to its function as` a striker or stinger and the ordinary kfunction as a tiring pin.

A general object of this invention is to provide any suitablevmeans for retarding the rotation ofthe impeller to the extent desired and although inertia of the impeller assembly is herein set forth as a preferred medium, it is also conceived that friction devices may be .usedwith a `corresponding decrease in reliance upon inertia` of nthe impeller.

A last object to be mentioned specifically is .to provide a fuze arming system which is susceptible to adjustment and modication to attain required functional characteristics by alteration of the various structural featuresto-a greater extent than in other fuzes of impeller type.

With these objects denitely in view, the present invention comprises the structure, combination and arrangement of elements as hereinafter described in the specification, pointed out in the appended claims, and illustrated in the drawing, wherein:

Figure l is a longitudinal sectional View of an end portion of a bomb with a fuze designed according to the instant invention operatively mounted thereon;

Figure 2 is an end elevational view of the fuze, taken from the lower end of the fuze as positioned in Figure l;

Figures 3 and 4 are transverse sectional views taken on the corresponding section lines 3-3 and 4 4 in Figure 1, and looking in the direction of the arrows.

2,748,708 fatented .lune 5, 1956 The operation of lthis fuze is based upon the concept'that the mass or inertia of a system may be so proportioned to theld'rivingforcelas to require a definite period of time for acceleration to some desired speed. Arming may be accomplished by centrifugal release of the restraining medium at some predetermined speed Within range of the operating speed. Air travel distance is determined by the Yimpeller-inertia relationship and vehicle velocity which may-ble proportioned insuch a manner as to obtain any combination of speed and acceleration within the limits of size -or starting inertia peculiar to a specic application. Increased impeller efficiency and decreased inertia will result in decreased times and arming distances, whileY decreased impeller eliiciency and increased inertia of the mass will give longer arming time or distance.

Similar characters of reference are used to designate similar or identical elements and portions throughout the specifica-tion and drawing.

VReferring now to the drawing, a bomb casing is fragmentarily indicated at and a booster at 12 with an externally threaded collar 14 upon which the internally threaded end 16 of the fuze body 1S is secured. It will be noted that said fuze body 18 is generally cylindrical with a stepped bore. An eccentric chamber portion 20 of this bore in the end 16 of the fuze body houses an arming member or rotor 22 which is mounted for pivotal movement about a pivot pin 24. This rotor 22 carries a primerzand has a stepped recess 2S, the centers of said V primer'and said recess 28'being equidistantfrom the pivot pin 24.' Therotor is biased to pivot from the position thereof shown in Figures l and 4 to a tiring position by a spring operatively mounted on said pivot pin. The recess 28 is considerably smaller in diameter than the main portion of the tiring pin 32 and the tiring pin functions as a key preventing the shifting of the rotor from the position shown in Figures l and 4 and preventing the primer 26 from being moved into yoperative position until the firing pin 32 has been shifted axially from the position thereof shown in the drawing.

A plate 34 is secured transversely of the fuze body, by means of screws 36, at one side of the rotor 22 and this `plate 34 supports what will be referred to as an inner bearing 38. The outer bearing is axially disposed in the apertured end plate 42 which has a peripheral attaching ange 44crimped in place in one end ofthe fuze body, as

Y indicated at 46,'.

sutlicient to overcome total friction between the ringpin and the rotor, between the ring pin and theouter bearing 44; and'between the inner bearing 38 andthe plate 34.

A plurality of stop pins 53 are slidably mounted in radial bores 60 and biased to move inwardly by springs 62 compressed between the pins and screw plugs 64. The shoulder or collar 56 on the tiring pin is engaged by the pins 58 to hold the tiring pin in the position indicated in Figure l. Air inlets 66 in the end plate 42 allow air, at air velocity during the descent of the bomb, to impinge upon the vanes 68 on the outer end of the impeller body, and the air exits through laterally disposed outlets 70.

In operation, when the inertia of the relatively massive irnpeller assembly has been overcome and a critical impeller rotation speed attained, the springs 62 will be overcome and the stop pins 58 will shift radially under centrifugal force to release the firing pin 32. The firing pin then moves axially under the influence of the spring 54 and the end 72 of the firing pin protrudes to function as a stinger which will minimize the possibility of malfunction upon impact and will determine the angle of impact through which the fuze will function. The rotor 22 is simultaneously released to shift under the inuence of the spring 30 to a position with the primer 26 aligned with the firing pin.

Since the arming speed is selected at some speed lower than the maximum rotating speed of the impeller, the release pins will be held radially outward so long as the air velocity is present. Upon contact, within the angle for which the fuze is designed to function, the firing pin will strike first firing the primer and booster. When the impeller assembly rotates, the firing pin rotates with it because of the proportionality of friction forces. However, the impeller can also rotate about the firing pin when sufficient retarding torque is applied to the stinger. Upon impact, the firing pin will move toward the primer at a greater irate than the rotating impeller mass will decelerate, and the firing pin shoulder will clear the release pins before they return to the central position. In the event that the pins have returned to the central position before the firing pin shoulder has cleared the release pins on the firing stroke, the pins will shear the relatively thin firing pin shoulder to fire the primer. The basic design of fuzes utilizing this combination of principles makes if inherently safe without numerous additional safety devices. The armed condition is readily apparent by the protrusion of the firing pin from the front of the fuze. When packed in inclosed clusters, no safety device is required since the fuze can arm only when subjected to continuous minimum air velocities for which it was designed.

While it is preferred that yretardation of the impeller be achieved, as described above, by the inertia of the impeller assembly alone, friction producing devices acting upon the impeller are proposed as equivalent in many respects and it is clear that such friction devices can be made adjustable so as to give further control of the arming function. The provision of such friction devices is proposed as coming within the general purview of this invention.

I claim:

1. In a fuze, a firing pin axially shifting from a safe to an armed position, a primer-carrying rotor having a recess formed therein, said firing pin engaging said recess to lock the rotor when said pin is in the safe position, a vaned impeller, journaled coaxially of and about said pin, a spring axially urging said pin to the armed position, and centrifugally releasable latch means carried by the impeller and directly engaging and holding said pin against the action of said spring.

2. In a fuze component, a fuze body, a firing pin axially slidable in said body from a safe to an arming position, an impeller journaled on said pin for spinning about the axis thereof and completely enclosing said pin when in said release means comprising a plurality of stop pins slidably mounted in radial bores and biased to move under the influence of centrifugal force on additional springs compressed between said stop pins and said impeller.

3. A fuze component as in claim 2, including an arming member, a primer fixed with said member and movable therewith from a first position out of alignment with said pin to a second position aligned therewith and for initiation thereby and additional second spring means urging said member to said second position, said pin when in safe position engaging and holding said member in its first position.

4. In a centrifugally-armed impact fuze, a fuze body, a firing pin slidable in said body from a first position within the confines thereof to a second position wherein one end of said pin is exposed beyond the fuze body for operation by impact, an arming member adapted to hold a primer and movable from a safe position wherein the primer is out of alignment with said pin, to an arming position wherein said pin initiates the primer in response to impact, means urging said pin to said second position, said pin when in said first position directly engaging and holding said member in safe position, an impeller in said body joulrnaled coaxially with and about said pin and centrifugally releasable latch means carried by said impeller and engaging said pin to normally hold the latter in said first position, said latch means comprising a plurality of stop pins slidably mounted in radial bores and biased to move under the inuence of centrifugal force on springs compressed between said stop pins and said impeller.

5. A fuze including an operatively mounted rotor having a primer thereon, a vaned impeller and a firing pin, said firing pin constituting an axis member for the impeller, said firing pin being held normally in locked position by releasable locking means comprising a plurality of stop pins slidably mounted in radial bores provided within the impeller, said stop pins being urged to move outwardly under the inuence of centrifugal force against compression springs positioned within said bores to bias said stop pins toward the inwardly locking positions, said releasable locking means normally holding the firing pin in engagement with said rotor so that the primer is retained out of alignment with said firing pin while the fuze is unarmed.

6. A fuze according to claim 5 including means to shift said firing pin axially so that one end lies outside of the fuze body to comprise a stinger.

7. A fuze according to claim 5 wherein said locking means additionally comprises a shoulder on said firing pin releasably engaged by said stop pins.

References Cited in the ile of this patent UNITED STATES PATENTS 1,229,669 Stuart June 12, 1917 2,068,708 Reed Jan. 26, 1937 2,396,245 Butler et al. Mar. 12, 1946 2,498,043 Lauritsen Feb. 2l, 1950 2,524,060 Liljegren Oct. 3, 1950 2,537,855 Porter Jan. 9, 1951 2,594,340 ORear Apr. 29, 1952 

